Shareholders Equity and Regulatory Matters - Schedule of comparison of the actual capital amounts and ratios (Details) $ in Thousands	Sep. 30, 2026 USD ($)	Dec. 31, 2025 USD ($)
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total capital (to risk weighted assets), Actual, Amount	$ 763,203	$ 628,120
Total capital (to risk weighted assets), Actual, Ratio	0.1245	0.1248
Total capital (to risk weighted assets), For Capital Adequacy Purposes, Amount	$ 643,628	$ 528,317
Total capital (to risk weighted assets), For Capital Adequacy Purposes, Ratio	0.105	0.105
Tier 1 capital (to risk weighted assets), Actual, Amount	$ 630,109	$ 501,426
Tier 1 capital (to risk weighted assets), Actual, Ratio	0.1028	0.0997
Tier 1 capital (to risk weighted assets), For Capital Adequacy Purposes, Amount	$ 521,032	$ 427,686
Tier 1 capital (to risk weighted assets), For Capital Adequacy Purposes, Ratio	0.085	0.085
Tier 1 capital (to average assets), Actual, Amount	$ 630,109	$ 501,426
Tier 1 capital (to average assets), Actual, Ratio	0.0955	0.0965
Tier 1 capital (to average assets), For Capital Adequacy Purposes, Amount	$ 263,971	$ 207,886
Tier 1 capital (to average assets), For Capital Adequacy Purposes, Ratio	0.04	0.04
Common equity tier 1 (to risk weighted assets), Actual, Amount	$ 563,949	$ 435,266
Common equity tier 1 (to risk weighted assets), Actual, Ratio	0.092	0.0865
Common equity tier 1 (to risk weighted assets), For Capital Adequacy Purposes, Amount	$ 429,086	$ 352,212
Common equity tier 1 (to risk weighted assets), For Capital Adequacy Purposes, Ratio	0.07	0.07
THIRD COAST BANK
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total capital (to risk weighted assets), Actual, Amount	$ 820,841	$ 660,607
Total capital (to risk weighted assets), Actual, Ratio	0.1341	0.1314
Total capital (to risk weighted assets), For Capital Adequacy Purposes, Amount	$ 642,860	$ 527,767
Total capital (to risk weighted assets), For Capital Adequacy Purposes, Ratio	0.105	0.105
Total capital (to risk weighted assets), To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 612,248	$ 502,636
Total capital (to risk weighted assets), To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	0.10	0.10
Tier 1 capital (to risk weighted assets), Actual, Amount	$ 768,866	$ 614,878
Tier 1 capital (to risk weighted assets), Actual, Ratio	0.1256	0.1223
Tier 1 capital (to risk weighted assets), For Capital Adequacy Purposes, Amount	$ 520,411	$ 427,240
Tier 1 capital (to risk weighted assets), For Capital Adequacy Purposes, Ratio	0.085	0.085
Tier 1 capital (to risk weighted assets), To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 489,798	$ 402,108
Tier 1 capital (to risk weighted assets), To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	0.08	0.08
Tier 1 capital (to average assets), Actual, Amount	$ 768,866	$ 614,878
Tier 1 capital (to average assets), Actual, Ratio	0.1166	0.1184
Tier 1 capital (to average assets), For Capital Adequacy Purposes, Amount	$ 263,706	$ 207,672
Tier 1 capital (to average assets), For Capital Adequacy Purposes, Ratio	0.04	0.04
Tier 1 capital (to average assets), To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 329,632	$ 259,591
Tier 1 capital (to average assets), To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	0.05	0.05
Common equity tier 1 (to risk weighted assets), Actual, Amount	$ 768,866	$ 614,878
Common equity tier 1 (to risk weighted assets), Actual, Ratio	0.1256	0.1223
Common equity tier 1 (to risk weighted assets), For Capital Adequacy Purposes, Amount	$ 428,573	$ 351,845
Common equity tier 1 (to risk weighted assets), For Capital Adequacy Purposes, Ratio	0.07	0.07
Common equity tier 1 (to risk weighted assets), To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 397,961	$ 326,713
Common equity tier 1 (to risk weighted assets), To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	0.065	0.065

Tier one risk based capital required for capital adequacy with buffer.

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Ratio of minimum Common Equity Tier 1 risk-based capital to risk-weighted assets required for capital adequacy as defined by regulatory framework.

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-Topic 942
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